1. Field of the Invention
The present invention relates to an apparatus and a method of chemical mechanical polishing (CMP) for a semiconductor wafer, more particularly, to a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus to improve the uniformity of the polished layer.
2. Description of the Related Art
Chemical Mechanical Polishing (CMP) is an industry-recognized process for leveling semiconductor wafers. The CMP process is used to achieve global planarization (planarization of the entire wafer). Both chemical and mechanical forces produce the desired polishing of the semiconductor wafer. For example, an insulator or a polysilicon layer filled in a shallow trench, an uneven dielectric layer, or an uneven metal layer can be planarized by CMP.
A CMP apparatus generally includes a rotating wafer carrier for holding a semiconductor wafer, a slurry supply system to feed slurry for CMP, and a rotating platen having a polishing pad on its upper surface. The semiconductor wafer is placed on a wafer carrier and pressed face down onto a polishing pad covered with a slurry of colloidal silica or alumina in deionized water.
The CMP apparatus having one slurry opening, used for global planarization has a problem related to polishing uniformity known as xe2x80x9cedge exclusionxe2x80x9d. Edge exclusion occurs when too much of the semiconductor wafer surface is polished. This causes the edge or outer portion of the semiconductor wafer to be unusable for integrated circuit fabrication. Wafer polish throughput and polish uniformity are important process parameters, because they also directly affect the number of integrated circuit chips that a fabrication facility can produce per unit equipment for a given period of time.
U.S. Pat. No. 6,227,947 discloses an apparatus and method for chemical mechanical polishing metal on a semiconductor wafer capable of achieving improved pad life. U.S. Pat. No. 5,578,529 discloses a method for using rinse spray bar in chemical mechanical polishing, providing complete and uniform wetting and rinsing of the polishing pad for an improved process. U.S. Pat. No. 6,284,092 discloses a CMP slurry atomization slurry dispense system to dispense the slurry toward the pad preferably as a stream or more preferably drops toward the pad surface. However, the problems related to polishing uniformity cannot be completely eliminated.
Therefore, a need has arisen for a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus that provides improved semiconductor wafer polish uniformity.
In view of the above disadvantages, an object of the invention is to provide a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus. The system is capable of improving wafer polish throughput and polish uniformity.
A further object of the invention is to achieve a desirable polish profile of the polished layer.
A further object of the invention is to provide a method for supplying slurry to the rotating platen of a chemical mechanical polishing apparatus capable of improving wafer polish throughput and polish uniformity.
Accordingly, the above objects are attained by providing a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus. The slurry supply system includes a wafer carrier configured to hold a semiconductor wafer to be polished; a supporting arm to support the wafer carrier; a slurry supplier connected to the supporting arm and located on the front edge of the rotating direction of the rotating platen so that the slurry supplier is positioned opposite the wafer carrier; and a plurality of openings formed on the slurry supplier to feed chemical mechanical polishing fluids, each of the openings individually supplied with individual control of the chemical mechanical polishing fluids.
A further object of the invention is to provide a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus. The slurry supplier is preferably arc-shaped.
In accordance with one aspect of the invention, there is provided a slurry supply system further comprising a pair of bars located at the ends of the slurry supplier coupling the slurry supplier to the supporting arm. Furthermore, the bars can be flexible so that the distance between the slurry supplier and the wafer carrier is controllable.
In accordance with another aspect of the invention, there is provided a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus. Each of the openings connects to a flow rate controller, such as a valve or a pump via a conduit.
In accordance with further aspect of the invention, there is provided a slurry supply system disposed above the rotating platen of a chemical mechanical polishing apparatus. The chemical mechanical polishing fluids are slurry and/or deionized water.
In accordance with yet another aspect of the invention, the slurry supplier can comprise a plurality of arc-shaped sections juxtaposed to each other and attached to the supporting arm.
In accordance with a still further aspect of the invention, there is provided a method for supplying slurry to the rotating platen of a chemical mechanical polishing apparatus. First, a slurry supply system having a plurality of openings capable of individually adjusting the flow rate of the slurry is provided. Then, at least one of the openings is selected to supply a slurry having a predetermined flow rate to the rotating platen of the chemical mechanical polishing apparatus.